Heat exchanger fin for air conditioner

ABSTRACT

The present invention discloses a heat exchanger fin having three rows of slit parts being arranged at the air inlet side and another three rows at the air outlet side relative to the centerline of heat transfer pipes  102 , in order to reduce the ventilating resistance, prevent the growth of a boundary layer and reduce a dead zone on the downstream of the heat transfer pipes  102  to thus increase heat transfer performance. The outer slit parts  111  and  111 ′; and  116  and  116 ′ at the air inlet side and at the air outlet side are formed in pairs. The middle slit parts  112  and  112 ′ at the air inlet side are formed in pairs and the middle slit part  114  at the air outlet side is formed in a unit. The inner slit parts  113  and  114  at the air inlet side and at the air outlet side are also formed in a unit. Therefore, the heat exchanger can reduce the airflow pressure drop and thus can increase air volume, and can improve the evaporation performance by increasing the heat transfer rate between the air and the fin surface.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a heat exchanger fin for an air conditioner, and more particularly, to a heat exchanger fin for an air conditioner which can reduce the airflow pressure drop and improve evaporation performance by arranging slit parts at the air inlet side and slit parts at the air outlet side in a different structure with a line passing through the center of each of the heat transfer pipes.

[0003] 2. Description of the Related Art

[0004] Generally, the indoor space of a building is contaminated by internal factors such as the breath of its residents, and thus needs to be periodically supplied with fresh air from the outside. Also, in hot summer weather or cold winter weather, a room has to be cooled or heated to an adequate temperature and has to maintain an adequate humidity suitable for human activities. For this purpose, most buildings are equipped with air conditioning systems.

[0005] Among the air conditioning systems for cooling a room, is used an air conditioner which cools a given indoor space by absorbing heat from the air during refrigerant evaporation. Typically, the air conditioner includes a compressor for compressing a refrigerant in the form of gas at a high temperature and high pressure, a condenser for liquefying the compressed refrigerant into a liquid state, and a heat exchanger evaporating the refrigerant expanded by an expansion valve. The cooled air, which is heat-exchanged while passing through the heat exchanger, is forcedly blown into the room requiring cooling by a blower fan in an air blower assembly.

[0006] The exchanger of such a type includes heat transfer pipes made of copper and the like connected with each other by a U-shaped band and fins made of aluminum and the like, and has a structure in which the air introduced between the fins are cooled by the refrigerant passing through the heat transfer pipes.

[0007] Recently, there is an increasing need for further miniaturization and high performance of heat exchangers. However, this is accompanied by the problems of deterioration of heat transmission performance and noise generation. Therefore, there have been attempts for achieving the miniaturization and high performance of heat exchangers, enhancing heat transmission performance and noise reduction.

[0008] Korean Patent No. 1991-3071 applied on Oct. 28, 1988 and registered on May 17, 1991 discloses a heat exchanger fin for enhancing heat transmission performance and noise reduction, simultaneously.

[0009] The shape of fins of the heat exchanger disclosed in the above-mentioned patent has a structure as shown in FIG. 1. That is to say, heat transfer pipes 2 are inserted into fin collars 12 formed by burring in a flat fin at predetermined intervals, and an airflows in the direction of the arrows A.

[0010] The fin 1 has a group of slit parts comprising a total of six rows of slit parts, that is, three on the air inlet side and another three on the air outlet side of the air current (A), between the two heat transfer pipes 2 that are arranged adjacent to each other in a direction perpendicular to the air current (A)

[0011] The slit parts at the upstream end and the downstream end comprise a pair of slit parts 14 and 24 separated by a central dividing flat portion 3a. Each of the other rows of slit parts includes one slit part 4. Openings 8, 18 and 28 of the six rows of slit parts are located perpendicular to the direction of air current (A).

[0012] The rising portions 5, 6, 15 and 25 on the heat transfer pipe 2 side of the slit parts 4, 14 and 24 are arranged so as to have angles of inclination in a direction along the outer tangential line (m) of the heat transfer pipe 2. Rising portions 16 and 26, on the central portion side of the pair of slit parts 14 and 24 at the upstream end or downstream end of air currents, are formed in a direction parallel to the rising portions 15 and 25. The pairs of slit parts 14 and 24 are formed in the shape of a parallelogram.

[0013] The slit parts in the six rows are formed alternately on both sides of the fin 1 with each intermediate flat portion placed therebetween.

[0014] In the above-described construction, the heat transfer rate between the air current and fin surfaces can be improved and thus heat exchange capacity can be increased. However, noise generation still remains and there is a limit to improving evaporation performance.

SUMMARY OF THE INVENTION

[0015] It is, therefore, an object of the present invention to provide a heat exchanger fin for an air conditioner which can reduce the airflow pressure drop and improve the evaporation performance by arranging slit parts at the air inlet side and slit parts at the air outlet side in a different structure with a line passing through the center of each of the heat transfer pipes.

[0016] In accordance with one embodiment of the present invention, a heat exchanger fin for an air conditioner comprising an air inlet side group of slit parts and an air outlet side group of slit parts being arranged between two heat transfer pipes, respectively, each of the slit parts being formed by a pair of rising portions whose ends project from the fin surface as well as a bridging portion spanning between the rising portions, central edge portions which are located at the inlet end portion of the air inlet side and an outlet end portion of the air outlet side, respectively, and intermediate flat portions being formed between adjacent those of the slit parts, is characterized in that: the air inlet side group of slit parts includes a pair of outer slit parts, a pair of middle slit parts, and an inner slit part sequentially from the inlet end, wherein each of the first rising portions of the outer slit parts and the middle slit parts is parallel to the direction l of air current (A) and each of the second rising portions of the outer slit parts and the middle slit parts are parallel to the outer tangential line (m) of the heat transfer pipes, and the opposite rising portions of the inner slit part are parallel to the direction of air current (A); and the air outlet side group of slit parts includes a pair of outer slit parts, a middle slit part, and an inner slit part sequentially from the outlet end, wherein the first rising portions of the outer slit parts are parallel to the direction l of air current (A) and the second rising portions are parallel to the outer tangential line (m) of the heat transfer pipes, the opposite rising portions of the middle slit parts are parallel to the outer tangential line (m) of the heat transfer pipes, and the opposite rising portions of the inner slit part are parallel to the direction of air current (A).

[0017] In accordance with another embodiment of the present invention, a heat exchanger fin for an air conditioner comprising a first group of slit parts arranged between the first heat transfer pipes and a second group of slit parts arranged between the second heat transfer pipes, each of the first and the second group of slit parts consisting of an air inlet side group of slit parts and an air outlet side group of slit parts arranged between two heat transfer pipes, respectively, each of the slit parts formed by a pair of rising portions whose ends project from the fin surface as well as a bridging portion spanning between the rising portions, central edge portions which are located at the inlet end portion of the air inlet side and an outlet end portion of the air outlet side, respectively, and intermediate flat portions being formed between adjacent those of the slit parts, is characterized in that: each of the air inlet side group of slit parts of the first and the second group of slit parts includes a pair of outer slit parts, a pair of middle slit parts, and an inner slit part sequentially from the inlet end, wherein each of the first rising portions of the outer slit parts and the middle slit parts are parallel to the direction l of air current (A) and each of the second rising portions of the outer slit parts and the middle slit parts are parallel to the outer tangential line (m) of the heat transfer pipes, and the opposite rising portions of the inner slit part are parallel to the direction of air current (A); and each of the air outlet side group of slit parts of the first and the second group of slit parts includes a pair of outer slit parts, a pair of middle slit parts, and an inner slit part sequentially from the outlet end, wherein the first rising portions of the outer and the middle slit parts are parallel to the direction l of air current (A) and the second rising portions are parallel to the outer tangential line (m) of the heat transfer pipes, and the opposite rising portions of the inner slit part are parallel to the direction of air current (A).

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which:

[0019]FIG. 1 is a plan view showing the shape of a heat exchanger fin for an air conditioner according to the prior art;

[0020]FIG. 2 is a perspective view showing the shape of a heat exchanger fin for an air conditioner according to a preferred embodiment of the present invention;

[0021]FIG. 3 is a plan view showing the shape of the heat exchanger fin for an air conditioner according to one embodiment of the present invention;

[0022]FIG. 4 is a sectional view taken along line IV-IV in FIG. 3;

[0023]FIG. 5 is a sectional view taken along line V-V in FIG. 3; and

[0024]FIG. 6 is a plan view showing the shape of a heat exchanger fin for an air conditioner according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0025] Preferred embodiments of a heat exchanger fin for an air conditioner of the present invention will now be described with reference to the accompanying drawings.

[0026] FIGS. 2 to 5 are views showing a heat exchanger fin according to the preferred embodiment of the present invention. Here, FIG. 2 is a perspective view showing the shape of a heat exchanger fin according to the present invention, FIG. 3 is a plan view showing the shape of the heat exchanger fin according to one embodiment of the present invention, FIG. 4 is a sectional view taken along line IV-IV in FIG. 3, and FIG. 5 is a sectional view taken along line V-V in FIG. 3.

[0027] The shape of the heat exchanger fin for an air conditioner according to the preferred embodiment of the present invention has a structure as illustrated in FIG. 2.

[0028] Heat transfer pipes 102 are inserted through a flat fin 100 at predetermined intervals, and airflows in the direction of the arrow (A) to be heat-exchanged with a refrigerant.

[0029] That is to say, a plurality of flat fins 100 are arranged in parallel at a predetermined interval, and a plurality of heat transfer pipes 102 in which refrigerants flow are inserted through each flat fin 100 in a perpendicular direction.

[0030] The flat fin 100 of the present invention has a group of slit parts comprising a total of six rows of slit parts: three (i.e. outer, middle and inner from the air inlet end) slit parts on the air inlet side; and another three (i.e. outer, middle and inner from the air inlet end) slit parts on the air outlet side of the air current (A), between the two heat transfer pipes 102.

[0031] Here, the air inlet side indicates the area in which air current (A) is introduced and the air outlet side indicates the area in which air current (A) is discharged, when viewed from the centerline C-C of the row of the heat transfer pipes 102.

[0032] Central edge flat portions 100 a located between the center area of the heat transfer pipes 102 are formed between a group of slit parts 111 and 111′; 112 and 112′ at the air inlet side and a group of slit parts 115 and 115′; and 116 and 116′ at the air outlet side.

[0033] Each of the slit parts (for example, 113 and 114 at the center) in each of the rows is formed by a pair of rising portions 113 a and 113 b; and 114 a and 114 b whose ends project from the fin surface as well as a bridging portion spanning the rising portions 113 a and 113 b; and 114 a and 114 b.

[0034] Additionally, the slit parts project alternately on the front face and the rear face of the flat fin 100, or only-on one of the faces of the flat fin 100.

[0035] That is, as illustrated in detail in FIGS. 2, 4 and 5, an outer slit parts 111 and 111′, an inner a slit part 113 and a middle slit part 115 project on the front face of the flat fin 100 sequentially from the shortest from the inlet end. A middle slit parts 112 and 112′, an inner slit parts 114 and an outer slit parts 116 and 116′ project on the rear face of the flat fin 100.

[0036] Intermediate flat portions 100 b are formed between the slit parts and each of the six rows of slit parts are arranged in parallel adjacent to each other.

[0037] Specifically, the group of slit parts 111 and 111′; 112 and 112′; and 113 at the air inlet side is constructed in such a manner that an inner slit part 113 is located adjacent to the centerline C-C of the heat transfer pipes 102, the outer slit parts 111 and 111′ are located at the inlet end portion, and a middle slit parts 112 and 112′ are located between the inner slit part 113 and the outer slit parts 111 and 111′.

[0038] The outer (first row of) slit parts 111 and 111′ and the middle (second row of) slit parts 112 and 112′ are formed in pairs, and the inner (third row of) slit part 113 is formed in a unit. First rising portions 111 a, 111 a′, 112 a and 112 a′of the outer slit parts 111 and 111′ and the middle slit parts 112 and 112′ are formed parallel to the direction l of air current (A), and second rising portions 111 b, 111 b′, 112 b and 112 b′ are formed in parallel to the outer tangential line (m) of the heat transfer pipes 102. Opposite rising portions 113 a and 113 b of the inner slit part 113 are parallel to the direction of the air current (A).

[0039] The group of slit parts 114; 115; and 116 and 116′ at the air outlet side is constructed in such a manner that the inner (fourth row of) slit part 114 is located adjacent to the centerline C-C of the heat transfer pipes

[0040]102, the outer (sixth row of) slit parts 116 and 116′ are located at the outlet end portion and a middle (fifth row of) slit part 115 is located between the inner slit part 114 and the outer slit parts 116 and 116′.

[0041] The outer slit parts 116 and 116′ are formed in pairs, being symmetrical to the outer slit parts 111 and 111′ at the inlet end portion relative to the centerline C-C of the heat transfer pipes 102. First rising portions 116 a and 116 a′ arranged parallel to the direction of air current (A) and second rising portions 116 b and 116 b′ are arranged parallel to the outer tangential line (m of FIG. 3) of the heat transfer pipe 102.

[0042] Each of the middle slit part 115 and the inner slit parts 114 is formed in a unit. Opposite Rising portions 115 a and 115 b of the middle slit part 115 are formed in parallel to the outer tangential direction of the heat transfer pipes 102 in the same manner as the second rising portions 116 b and 116 b′ of the outer slit parts 116 and 116′. Opposite rising portions 114 a and 114 b of the inner slit part 114 are formed in parallel to the direction of air current (A).

[0043] By allowing the air introduced from the air inlet end to the first and second rows of slit parts 111 and 111′; and 112 and 112′ to flow uniformly on the heat transfer pipes 102 and the base surface of the flat fin 100, the heat transfer efficiency is enhanced. Also, by constructing the middle slit part 115 at the outlet side in a unit, it is possible to prevent heat transfer capacity from being decreased due to the continuous growth of a temperature boundary layer on the base surface located between the slit parts spaced apart from each other.

[0044] When observing an enlarged view of the surface of the area linking a base surface and rising portions of a projecting portion, this area protrudes from the base surface to the rising portions of the projecting portion. Thus the surface roughness giving resistance to airflow is increased relative to the number of rising portions on the base surface. The fin surface of the rising portions is bent, not consistent with a stream flow, whereby the ventilating resistance is increased.

[0045] Therefore, the middle slit part 115 at the air outlet side is formed in a unit so that the number of rising portions is minimized, i.e., two in order to reduce the ventilating resistance. As another effect of constructing the middle slit part 115 at the air outlet side in a unit, the reduction of airflow and the scattering of condensate are prevented by smoothly discharging the condensate.

[0046] Namely, in a wet coil state which produces condensate, if the projecting portion is separated, the condensate water is locked in a vent hole of the projecting portion by the surface tension of the projecting portion, thereby making it difficult to discharge the condensate. This causes a decrease of airflow by a rapid increase of ventilating resistance and greatly reduces the cooling performance. However, in the present invention, by forming the middle slit part 115 at the air outlet side in a unit, condensate is smoothly discharged.

[0047] Since a dead zone formed on the heat transfer pipe at the exit side causes a loss of flow pressure and a loss in heat transfer efficiency, it must be minimized to avoid a decrease in ventilating resistance and heat transfer efficiency. In the present invention, the second rising portions 116 b and 116 b′ are arranged adjacent to the heat transfer pipes 102 in order to form the outer slit parts 116 and 116′ located next to the middle slit part 115 at a location reducing the dead zone on the downstream of the heat transfer pipe.

[0048] In this case, if the outer slit parts 116 and 116′ are formed integrally, the rigidity of the bridging portion becomes weak according to an increase of the length of the bridging portion, whereby the bridging portion is bent or it is vibrated by airflow, that is, abnormal noise is generated. Thusly the outer slit parts 116 and 116′ are spaced apart in order to reduce the dead zone on the downstream of the heat transfer pipe, whereby the rigidity of the bridging portion is maintained.

[0049] The first embodiment is not limited to the example of the heat transfer pipes being disposed in a row parallel to the direction of air current, but may also be applied to the heat transfer pipes being disposed in plural rows parallel to the direction of air current. Also, in this case, the shape of the slit parts according to the present invention may be formed in plural rows parallel to each other relative to the line passing through the center of the heat transfer pipes.

[0050] Referring to FIG. 6, a heat exchanger according to a second embodiment of the present invention will now be described in detail.

[0051]FIG. 6 is a plan view showing the shape of a heat exchanger fin for an air conditioner according to another embodiment of the present invention.

[0052] The shape of the flat fin 200 of the heat exchanger according to the present embodiment has a structure of two rows type heat transfer pipes 202 and 202′ as illustrated therein. That is, the flat fin 200 of this embodiment comprises a first group of slit parts being arranged between the first heat transfer pipes 202′ and a second group of slit parts being arranged between the second heat transfer pipes 202. Each of the first and the second group of slit parts consists of an air inlet side group of slit parts and an air outlet side group of slit parts being arranged between the first and the second heat transfer pipes 202′ and 202, respectively.

[0053] Each of the heat transfer pipes 202′ and 202 is inserted through a flat fin 200, and airflows in the direction of the arrow (A) to thus be heat-exchanged with refrigerant.

[0054] That is to say, a plurality of flat fins 200 are arranged in parallel at predetermined intervals, and a plurality of heat transfer pipes 202 and 202′ in which refrigerants flow are inserted through each flat fin 200 in a perpendicular direction.

[0055] The flat fin 200 of the present embodiment has two group of slit parts comprising each of sixth rows of slit parts, that is, six on the first group of slit parts between the first heat transfer pipes 202′ and another six on the second group of slit parts between the second heat transfer pipes 202.

[0056] Here, the air inlet side of the first and second group of slit parts indicates the area in which air current (A) is introduced and the air outlet side indicates the area in which air current (A) is discharged, with respect to the central portion between the centerline C1-C1 of the first heat transfer pipes 202′ and the centerline C-C of the second heat transfer pipes 202.

[0057] Although, the slit parts of the flat fin 200 will be described for the second group of slit parts between the second heat transfer pipes 202, it should be understood that the first group of slit parts between first the heat transfer pipes 202′ has the same construction as those of the second group of slit parts.

[0058] Central edge flat portions 200 a located between the center area of the heat transfer pipe 202 are formed between a group of slit parts 211 and 211′; and 212 and 212′ at the air inlet side and a group of slit parts 215 and 215′; and 216 and 216′ at the air outlet side, with respect to the centerline C-C of the second heat transfer pipes 202.

[0059] Each of the slit parts (for example, 213 and 214 at the center) in each of the rows is formed by a pair of rising portions 213 a and 213 b; and 214 a and 214 b whose ends project from the fin surface as well as a bridging portion spanning the rising portions 213 a and 213 b; and 214 a and 214 b.

[0060] As above-mentioned in the first embodiment, the slit parts project alternately on the front face and the rear face of the flat fin 200, or only on one of the faces of the flat fin 200.

[0061] That is, a outer slit parts 211 and 211′, a inner a slit part 213 and a middle slit parts 215 and 215′ project on the front face of the flat fin 200 sequentially from the one shortest from the front end portion of the outlet side. A middle slit parts 212 and 212′, an inner slit parts 214 and an outer slit parts 216 and 216′ project on the rear face of the flat fin 200.

[0062] Intermediate flat portions 200 b are formed between each of the slit parts and the six rows of slit parts are arranged in parallel adjacent to each other.

[0063] Specifically, the group of slit parts 211 and 211′; 212′ and 212′; and 213 at the air inlet side is constructed in such a manner that an inner slit part 213 is located adjacent to the centerline C-C of the heat transfer pipes 202, the outer slit parts 211 and 211′ are located at the inlet end portion (i.e. central portion between the centerlines C1-C1 and C-C of the first and the second heat transfer pipes 202′ and 202 in FIG. 6), and a middle slit parts 212 and 212′ are located between the inner slit part 113 and the outer slit parts 111 and 111′.

[0064] The outer slit parts 211 and 211′ and the middle slit parts 212 and 212′ are formed in pairs, and the inner slit part 213 is formed in a unit. First rising portions 211 a, 211 a′, 212 a and 212 a′ of the outer slit parts 211 and 211′ and the middle slit parts 212 and 212′ are formed parallel to the direction of air current (A), and second rising portions 211 b, 211 b′, 212 b and 212 b′ are formed in parallel to the outer tangential line (m) the heat transfer pipe 202.

[0065] The group of slit parts 214; 215 and 215′; and 216 and 216′ at the air outlet side is constructed in such a manner that the inner slit part 214 is located adjacent to the centerline C-C of the heat transfer pipes 202, the outer slit parts 216 and 216′ are located at the air outlet side and the middle slit parts 215 and 215′ is located between the fourth row slit part 214 and the outer slit parts 216 and 216′.

[0066] The inner slit part 214 is formed in a unit. Opposite rising portions 214 a and 214 a′ are formed in parallel to the direction of air current (A).

[0067] The outer slit parts 216 and 216′ are formed in pairs, being symmetrical to the outer slit parts 211 and 211′ at the inlet side relative to the centerline C-C of the heat transfer pipes 202. First rising portions 216 a and 216 a′ arranged parallel to the direction l of air current (A) and second rising portions 216 b and 216 b′ are arranged parallel to the outer tangential line (m) of the heat transfer pipe 202.

[0068] The middle slit parts 215 and 215′ are formed in pairs, being asymmetrical to the middle slit parts 212 and 212′ at the inlet side relative to the centerline C-C of the heat transfer pipes 202. First rising portions 215 a and 215 a′ arranged parallel to the direction l of air current (A) and second rising portions 215 b and 215 b′ are arranged parallel to the outer tangential line (m) of the heat transfer pipe 202.

[0069] To reduce the dead zone on the downstream of the heat transfer pipes 202 which causes a decrease of heat transfer -rate and an increase of pressure loss, the spacing between the first rising portions 211 a and 211 a′ of the outer slit parts 211 and 211′ at the air inlet side is formed larger than the spacing between the first rising portions 212 a and 212 a′ of the middle slit parts 212 and 212′, and the second rising portions 211 b and 211 b′; and 212 b and 212 b′ of the outer slit parts 211 and 211′ and the middle slit parts 212 and 212′ are arranged more adjacently than the prior art approximately the same distance from the heat transfer pipes 202.

[0070] Likewise, the spacing between the first rising portions 216 a and 216′ of the outer slit parts 216 and 216′ at the air outlet side are formed larger than the spacing between the first rising portions 215 a and 215 a′ of the middle slit parts 215 and 215′, and the second rising portions 216 b, 216 b′, 215 b and 215 b′ of the outer slit parts 216 and 216′ and the middle slit parts 215 and 215′ are arranged adjacently approximately the same distance from the heat transfer pipes 202.

[0071] At the same time, the first rising portion 216 a′ of at least one 216′ of the outer slit parts 216 and 216′ and the first rising portion 215 a′ of at least one 215′ of the middle slit parts 215 and 215′ are arranged in parallel in the direction l of air current (A).

[0072] At this time, the middle slit parts 212 and 212′ at the air outlet side and the fifth slit parts 215 and 215′ at the air outlet side are arranged parallel to a diagonal direction relative to the centerline C-C of the heat transfer pipes 202. That is, the middle slit parts 215 and 215′ at the outlet side of the first and the second group of slit parts are formed in asymmetrically with the middle slit parts 212 and 212′ at the inlet side relative to the centerline of the second heat transfer pipes 202.

[0073] Next, in the structure of the shape of the constructed fin, the structure of heat transfer pipes 202 and 202′ arranged in two rows will be described.

[0074] As illustrated in FIG. 6, the flat fin 200 is divided into an inlet side row portion and an outlet side row portion with a center as a boundary therebetween. The first and the second heat transfer pipes 202 and 202′ are inserted through each row portion perpendicular to the principal direction l of air current (A).

[0075] These heat transfer pipes 202 and 202′ are arranged in such a manner that the inlet side rows and the outlet side rows do not overlap in the direction of the air current (A).

[0076] Meanwhile the air inlet side rows and the air outlet side rows are arranged in the approximately same pattern with a phase difference relative to the central portion between the centerline C1-C1 of the first heat transfer pipes 202′ and the centerline C-C of the second heat transfer pipes 202.

[0077] That is, the group of slit parts in the air inlet side rows arranged relative to the centerline C-C of the heat transfer pipe 202 and the group of slit parts in the air outlet side rows arranged relative to the centerline C1-C1 of the heat transfer pipe 202′ are arranged in the same pattern at intervals the same as the phase difference of the heat transfer pipes 202 and 202′, except for the asymmetrical location of the middle slit parts at the inlet side and the outlet side.

[0078] As described above, according to the first embodiment of the present invention, three rows of slit parts are arranged respectively at the air inlet side and the air outlet side relative to the centerline of the heat transfer pipes in the first and second rows at the air inlet end. Each of the inner slit parts at the air inlet side and the air outlet side is formed in a unit, and the outer slit parts are formed in pairs. In case of the middle slit parts arranged between the inner slit parts and the outer slit parts, each of the middle slit parts at the air inlet side are formed in a unit, and the middle slit parts at the air outlet side are formed in pairs. By this construction, the airflow pressure drop can be decreased, the air volume can be increased, and the heat transfer rate between the air and the fin surface can be increased to thus increase the evaporation performance.

[0079] According to the second embodiment of the present invention, six rows of slit parts are arranged respectively at the air inlet side and the air outlet side relative to the central portion between the centerlines of the heat transfer pipes. For example, each of the inner slit parts at the air outlet side and the air outlet side are formed in a unit, and the outer slit parts are formed in pairs. In case of the middle slit parts arranged between the inner slit parts and the outer slit parts, each of the middle slit parts at the air inlet side is formed in a unit, and the middle slit parts at the air outlet side are formed in pairs. By this construction, the airflow pressure drop can be decreased, noise can be reduced, and the heat transfer rate between the air and the fin surface can be increased to thus increase the evaporation performance. 

What is claimed is:
 1. A heat exchanger fin for an air conditioner comprising an air inlet side group of slit parts and an air outlet side group of slit parts being arranged between two heat transfer pipes, respectively, each of the slit parts being formed by a pair of rising portions whose ends project from the fin surface as well as a bridging portion spanning between the rising portions, central edge portions which are located at an inlet end portion of the air inlet side and an outlet end portion of the air outlet side, respectively, and intermediate flat portions being formed between adjacent those of the slit parts, the heat exchanger fin characterized in that: the air inlet side group of slit parts includes a pair of outer slit parts, a pair of middle slit parts, and an inner slit part sequentially from the inlet end, wherein each of the first rising portions of the outer slit parts and the middle slit parts is parallel to the direction l of air current (A) and each of the second rising portions of the outer slit parts and the middle slit parts are parallel to the outer tangential line (m) of the heat transfer pipes, and the opposite rising portions of the inner slit part are parallel to the direction of air current (A); and the air outlet side group of slit parts includes a pair of outer slit parts, a middle slit part, and an inner slit part sequentially from the outlet end, wherein the first rising portions of the outer slit parts are parallel to the direction l of air current (A) and the second rising portions are parallel to the outer tangential line (m) of the heat transfer pipes, the opposite rising portions of the middle slit parts are parallel to the outer tangential line (m) of the heat transfer pipes, and the opposite rising portions of the inner slit part are parallel to the direction of air current (A).
 2. The heat exchanger fin of claim 1, characterized in that the spacing between the first rising portions of the outer slit parts at the air inlet side is larger than the spacing between the first rising portions of the middle slit parts, whereby the second rising portions of the outer slit parts and the middle slit parts are arranged more adjacently, but approximately the same distance from the heat transfer pipes.
 3. The heat exchanger fin of claim 1, characterized in that the second rising portions of the middle slit parts at the air inlet side and the opposite rising portions of the middle slit parts are arranged adjacent to each other approximately the same distance from the heat transfer pipes.
 4. The heat exchanger fin of claim 1, characterized in that the slit parts project alternately on the front face and the rear face of the flat fin, or only on one of the faces of the flat fin.
 5. A heat exchanger fin for an air conditioner comprising a first group of slit parts being arranged between the first heat transfer pipes and a second group of slit parts being arranged between the second heat transfer pipes, each of the first and the second group of slit parts consisting of an air inlet side group of slit parts and an air outlet side group of slit parts being arranged between two heat transfer pipes, respectively, each of the slit parts being formed by a pair of rising portions whose ends project from the fin surface as well as a bridging portion spanning between the rising portions, central edge portions which are located at an inlet end portion of the air inlet side and an outlet end portion of the air outlet side, respectively, and intermediate flat portions formed between adjacent those of the slit parts, the heat exchanger fin characterized in that: each of the air inlet side group of slit parts of the first and the second group of slit parts includes a pair of outer slit parts, a pair of middle slit parts, and an inner slit part sequentially from the inlet end, wherein each of the first rising portions of the outer slit parts and the middle slit parts are parallel to the direction l of air current (A) and each of the second rising portions of the outer slit parts and the middle slit parts are parallel to the outer tangential line (m) of the heat transfer pipes, and the opposite rising portions of the inner slit part are parallel to the direction of air current (A); and each of the air outlet side group of slit parts of the first and the second group of slit parts includes a pair of outer slit parts, a pair of middle slit parts, and an inner slit part sequentially from the outlet end, wherein the first rising portions of the outer and the middle slit parts are parallel to the direction l of air current (A) and the second rising portions are parallel to the outer tangential line (m) of the heat transfer pipes, and the opposite rising portions of the inner slit part are parallel to the direction of air current (A).
 6. The heat exchanger fin of claim 5, characterized in that the spacing between the first rising portions of the outer slit parts of the first and the second group of slit parts at the air inlet side is formed larger than the spacing between the first rising portions of the middle slit parts, and the second rising portions of the outer slit parts and the middle slit parts are arranged more adjacently approximately the same distance from the heat transfer pipe, respectively; and the first rising portion of at least one of the outer slit parts of the first and the second group of slit parts at the air inlet side and the first rising portion at least one of the middle slit parts are arranged in parallel in the direction of air current.
 7. The heat exchanger fin of claim 5, characterized in that the spacing between the first rising portions of the outer slit parts of the first and the second group of slit parts at the air outlet side is formed larger than the spacing between the first rising portions of the middle slit parts, and second rising portions of the outer slit parts and the middle slit parts of the first and the second group of slit parts are arranged more adjacently approximately the same distance from the heat transfer pipe, respectively; and the first rising portion of at least one of the outer slit parts of the first and the second group of slit parts at the air outlet side and the first rising portion at least one of the middle slit parts are arranged in parallel in the direction of air current.
 8. The heat exchanger fin of claims 5, characterized in that the outer slit parts at the air outlet side of the first and the second group of slit parts are formed in symmetrically with the outer slit parts at the inlet side relative to the centerline of the first and second heat transfer pipes, respectively.
 9. The heat exchanger fin of claims 5, characterized in that the middle slit parts at the air outlet side of the first and the second group of slit parts are formed in asymmetrically with the middle slit parts at the inlet side relative to the centerline of the first and second heat transfer pipes, respectively. 